1. Field of the Invention
This invention relates to a method of and apparatus for electrically heating a bottom unloading valve of a railroad tank car that is held open by liquids solidified therein or around the valve. The heating unit liquefies solidified fluids, making the valve manually operable.
2. Description of the Prior Art
It has been my experience that when railroad tank cars are emptied through bottom unloading valves which are then left completely or partially open, these valves may become locked in that position. This occurs when the liquids that they had been carrying have the characteristics of solidifying at ambient temperature. The reason is simply these fluids get trapped in and around the moveable components of the valve which, when the fluids become solidified, make the valve manually inoperable. Examples of some of the chemicals that are ordinarily transported in a liquid or molten state but become solidified fluids at ambient temperature (e.g. 70.degree. F or 21.degree. C), are sulfur (melting point (m.p.) 112.8.degree. C); maleic anhydride (m.p. 58.degree. C); phenol (m.p. 40.6.degree. C); and phthalic anhydride (m.p. 131.2.degree. C).
At locations where steam heat is provided, these locked-open valves may be made manually operable by passing steam through conduits located throughout the tank car. However, there are times and places where steam is not available. Additionally, it is inefficient to heat the entire tank car when only one valve requires it.
Others have proposed electrically heating tank cars through impedance or resistance heating. However, this approach is expensive and inefficient to use as in the case of steam, since the entire tank car is heated. Another difficulty, like that of steam, is adequate electrical power may not be available.
Another possible solution might be to replace manually operated valves with automatic closing ones; that is, valves which immediately close after the car is unloaded. The problem here is that manual valves are in widespread use now, and would be quite costly to replace. On the other hand, the heating device described in detail below is an apparatus that can be used to free the valve of almost any manufacturer, located on any tank car.